Tokyo: Beijing is jeopardising peace in a row with Tokyo over disputed islands, Japan`s defence minister said today, days after China warned any bid to shoot down its drones would constitute "an act of war".

Itsunori Onodera`s comments are likely to further heighten fears that the two countries could be sliding towards conflict over the outcrops in the East China Sea and come on the day that China showed off its fleet of nuclear-powered submarines.

"I believe the intrusions by China in the territorial waters around the Senkaku islands fall in the `grey zone` (between) peacetime and an emergency situation," Onodera told reporters in Tokyo.

The two sides have been at loggerheads over the island chain, which China claims and calls the Diaoyus, since Tokyo bought three of them from their private Japanese owner in September 2012.

But the comments from Onodera following those from China`s defence ministry at the weekend, appear to have taken the verbal fisticuffs to a new level.

China`s coastguard yesterday sent four vessels into the waters around the islands, where they stayed for two hours, shadowed by their Japanese counterparts.
That came after three consecutive days in which Tokyo scrambled jets to meet Chinese aircraft as they traversed a strait leading to the Pacific. They did not enter Japanese airspace.

"They were two early-warning aircraft and two bombers," Onodera told reporters today.

"It was unusual that so many aircraft flew between the Okinawan main island and Miyako island. We consider that it is also very unusual that it occurred for three days in a row.

"We understand that it is one of the trends showing that China is now vigorously expanding its areas of activities, including into the open ocean."